PCI/PM: add PCIe runtime D3cold support

This patch adds runtime D3cold support and corresponding ACPI platform
support.  This patch only enables runtime D3cold support; it does not
enable D3cold support during system suspend/hibernate.

D3cold is the deepest power saving state for a PCIe device, where its main
power is removed.  While it is in D3cold, you can't access the device at
all, not even its configuration space (which is still accessible in D3hot).
Therefore the PCI PM registers can not be used to transition into/out of
the D3cold state; that must be done by platform logic such as ACPI _PR3.

To support wakeup from D3cold, a system may provide auxiliary power, which
allows a device to request wakeup using a Beacon or the sideband WAKE#
signal.  WAKE# is usually connected to platform logic such as ACPI GPE.
This is quite different from other power saving states, where devices
request wakeup via a PME message on the PCIe link.

Some devices, such as those in plug-in slots, have no direct platform
logic.  For example, there is usually no ACPI _PR3 for them.  D3cold
support for these devices can be done via the PCIe Downstream Port leading
to the device.  When the PCIe port is powered on/off, the device is powered
on/off too.  Wakeup events from the device will be notified to the
corresponding PCIe port.

For more information about PCIe D3cold and corresponding ACPI support,
please refer to:

- PCI Express Base Specification Revision 2.0
- Advanced Configuration and Power Interface Specification Revision 5.0

[bhelgaas: changelog]
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>
Originally-by: Zheng Yan <zheng.z.yan@intel.com>
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 40 insertions, 4 deletions

diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 7c576b9aa01..3a7eefcb270 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -101,12 +101,48 @@ static int pcie_port_resume_noirq(struct device *dev)
 }
 
 #ifdef CONFIG_PM_RUNTIME
-static int pcie_port_runtime_pm(struct device *dev)
+struct d3cold_info {
+        bool no_d3cold;
+        unsigned int d3cold_delay;
+};
+
+static int pci_dev_d3cold_info(struct pci_dev *pdev, void *data)
+{
+        struct d3cold_info *info = data;
+
+        info->d3cold_delay = max_t(unsigned int, pdev->d3cold_delay,
+                                   info->d3cold_delay);
+        if (pdev->no_d3cold)
+                info->no_d3cold = true;
+        return 0;
+}
+
+static int pcie_port_runtime_suspend(struct device *dev)
+{
+        struct pci_dev *pdev = to_pci_dev(dev);
+        struct d3cold_info d3cold_info = {
+                .no_d3cold      = false,
+                .d3cold_delay   = PCI_PM_D3_WAIT,
+        };
+
+        /*
+         * If any subordinate device disable D3cold, we should not put
+         * the port into D3cold.  The D3cold delay of port should be
+         * the max of that of all subordinate devices.
+         */
+        pci_walk_bus(pdev->subordinate, pci_dev_d3cold_info, &d3cold_info);
+        pdev->no_d3cold = d3cold_info.no_d3cold;
+        pdev->d3cold_delay = d3cold_info.d3cold_delay;
+        return 0;
+}
+
+static int pcie_port_runtime_resume(struct device *dev)
 {
         return 0;
 }
 #else
-#define pcie_port_runtime_pm    NULL
+#define pcie_port_runtime_suspend       NULL
+#define pcie_port_runtime_resume        NULL
 #endif
 
 static const struct dev_pm_ops pcie_portdrv_pm_ops = {
@@ -117,8 +153,8 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
         .poweroff       = pcie_port_device_suspend,
         .restore        = pcie_port_device_resume,
         .resume_noirq   = pcie_port_resume_noirq,
-        .runtime_suspend = pcie_port_runtime_pm,
-        .runtime_resume = pcie_port_runtime_pm,
+        .runtime_suspend = pcie_port_runtime_suspend,
+        .runtime_resume = pcie_port_runtime_resume,
 };
 
 #define PCIE_PORTDRV_PM_OPS     (&pcie_portdrv_pm_ops)